The embrace (some might say exaltation) of butter is, in some respects, what sets the Primal eating plan apart from strict paleo . It is essentially pure animal fat  with only minor traces of dairy proteins and sugars remaining, and for that reason I consider it a worthwhile staple. But, to answer the question posed in the title, not all butter is created equal. Most of us are in agreement that the nutritional content of the animal’s flesh depends on the content of its diet, and the same goes for butter.
We’ve covered similar ground with other foods – olive oil , cheese , chocolate , to name a few – but butter’s special. A quick glance around the forum  and other online paleo/Primal/real food communities reveals that people are mad for butter. Perhaps it’s because we’re subject to a steady barrage of anti-butter propaganda from day one on this earth; perhaps it’s due to the fact that the stuff tastes like heaven and goes with nearly everything. Whatever the reason, butter knowledge is important.
Grass-Fed vs. Grain-Fed
The eternal battle rages on. While the grass-fed camp may be outnumbered, they are plucky, pugnacious fighters with superior armament, training, and tactics. Once they finish off grain-fed butter in Spartans-at-Thermopylae  fashion, I expect them to make short work of margarine. Here’s why it’s so lopsided:
Conjugated Linoleic Acid (CLA) Content
CLA is a funny fatty acid. It’s actually a trans-fat , but it’s a good, naturally occurring one. Instead of a group of candle wax makers creating trans-fats in industrial vats by hydrogenating cottonseed oil into disgusting, technically edible faux-butter, the special digestive systems of grass-fed ruminants produce CLA internally. The resulting trans-fat – which has been linked to superior heart health , suppression of tumors , reduced belly fat  (although in pigs, I’m not sure that’s what we’re after!), and greater fat loss in the obese and overweight  – pops up in the flesh and dairy of the animal. As far as cows go, pasture feeding leads to dairy CLA levels 3-5 times that of grain-fed cattle (PDF).
Winner: Grass-fed Butter
We’re drawn to colorful things, especially foods. Bright berries , verdant greens , multicolored fruits and peppers  – these are the naturally occurring foods with the most phytonutrients. In fact, the actual dyes responsible for providing color to vegetation, like the blue in blueberry, are also usually antioxidants. Funny how that works out, eh? The same is true for butter. You ever notice how grass-fed butter actually looks like butter? It’s a deep yellow, sometimes bordering on orange, whereas grain-fed butter is white and waxy. It’s yellow because it has more carotene (think carrot, think orange) and Vitamin A . It’s got more carotene because it comes from cows that eat fresh vegetation rich in the stuff. From pasture to ruminant to digestive tract to butterfat to butter to you. Grain-fed? From the study I just linked, even back in 1933 they understood that “the oil cakes and cereals in common use are incapable of bringing about this result” of yellow, vitamin-rich butter.
Vitamin K2 , in case you weren’t aware, appears to reduce, prevent, or even counteract arterial plaque, and it helps the body use calcium correctly and effectively. Vitamin K2 is another vital component of grass-fed butter. As Dr. Weston Price observed, only cows subsisting on fresh green grass produced butter imbued with significant levels of the all-important “Activator X,” which most people agree is vitamin K2. Cow stomach fermentation turns K1 (found in leafy greens, like kale, chard, spinach, and, yes, leaves of grass) into K2, which then shows up in the dairy fat. How much Vitamin K1 do you think there is in corn? Not much at all  (PDF).
Winner: Grass-fed Butter
Fatty Acid Composition
Whether it’s grass-fed or grain-fed, butter is rich in saturated  (about 2/3) and monounsaturated  (just under 1/3) fat. The rest is polyunsaturated , but this is where grass-fed and grain-fed really differ. Cows raised on pasture produce milk fat with an omega 6  to omega 3  ratio of 1 . Yes, equal amounts. A balance. Grain-fed cows, on the other hand, produce a ratio tilted heavily toward omega 6. It’s true that we’re talking about relatively miniscule amounts of polyunsaturated fats here, but I prefer the balanced ratio. And if you’re putting away as much butter as I can, those insignificant amounts of omega 6 can begin to add up.
Winner: Grass-fed Butter
Flavor is usually a subjective determination. What tastes better is entirely a matter of personal opinion, right? Not in the case of butter. Grass-fed butter tastes objectively better using any parameter. Creaminess? Smooth, yellow grass-fed butter can be eaten and enjoyed like candy. Richness? Grain-fed is weak and insipid in comparison. Mouth feel? Grass-fed coats the interior (in a pleasant way), while grain-fed comes off as watery and unnatural.
Winner: Grass-fed Butter
All that said, grain-fed butter is still a better option than conventional cooking fats, like vegetable oil or margarine . I still request restaurant food to be cooked in butter, completely aware that it’s probably white as a ghost and totally grain-fed. The saturated fat in regular butter isn’t any less stable.
Grass-fed isn’t as tough to find as you might think, though. And even if it’s more expensive, it’s still cheaper than shelling out the dough for exclusively grass-fed meat. In fact, for those of you who can’t regularly eat pastured meat, eating lean cuts of conventional meat cooked in a quality grass-fed butter is a great compromise.
Watch out for these brands near you:
A favorite, fairly easy-to-find brand is Kerrygold , an Irish dairy whose cows are all pastured and whose butter is incredible. I get mine for $2.69 at Trader Joe’s, but I’ve seen it in basic and specialty grocery stores, too (albeit for slightly higher prices). Look for the silver foil (unsalted) and gold foil (salted) packages.
Anchor butter is another tasty one. It hails from New Zealand, land of reliably grass-fed lamb, and I’ve seen it at Whole Foods for a reasonable price. If you can’t find it there, you could always order online  in bulk. Just freeze the extras.
Organic Valley has a seasonal pastured, cultured, salted butter that usually appears in spring, which is when the grass is at its greenest. I’ve had it a few times. It’s good and a bit tangy, and it comes in a green foil package. Skip the regular Organic Valley stuff, which gets some grain.
Check farmers’ markets. If you’ve got a dairy stall, you’ve probably got access to good butter. Talk to the producers about the cows’ diet.
Learn the slang that’ll help you blend in with the cool kids at the next Weston A. Price Foundation meet-up.
What is cultured butter?
Cultured butter is traditionally made from fermented, or soured, cream. It’s not actually the butterfat that ferments, but rather the trace amounts of lactose sugars present. Nowadays, though, most commercial cultured butter is “cultured” by the incorporation of bacterial cultures. “European style” butter is cultured butter.
What is “sweet butter”?
Historically, sweet cream butter came from fresh cream, rather than soured or fermented  cream. Relative to cultured butter, it’s rather “sweet.” These days, it’s often just another way to describe unsalted butter. Sweet butter is better for cooking, as most recipes assume the use of unsalted butter. Also, since salt is a preservative, sweet butter tends to be fresher (since it has to be, having no preservatives).
What is clarified butter?
Heat butter until it melts, let it cool and settle, then skim off the top layer of whey protein and pour off the butterfat, leaving the casein proteins on the bottom – you’ve got clarified butter.
What about ghee?
Ghee  is basically pure butterfat, rendered down and stricken of all lactose and dairy proteins. It’s ultra-clarified butter in that it reaches a temperature high enough to cook off the water and brown the milk solids, which imparts a nutty flavor to the finished product. Properly made, ghee can stay on the counter for about a year without going bad. If you’ve got one, check your local Indian grocer. They’ll have huge tubs of intensely yellow ghee for sale. Is it all grass-fed? I’ve no idea, and the rich color isn’t a reliable indicator since the color could come from the browned milk solids. Anyone know for sure?
There are clear winners and losers in life. Grass-fed butter wins handily and grain-fed loses. There’s not much more to say other than get out there and find yourself a decent source of grass-fed butter!
Thanks for reading, everyone, and Grok on!